Fix server side relationship search

[samiksengupta]

This fixes the issue with Voyager's server side searching.

This potentially fixes #5645 #5635 #5433 #5412

This issue can be recreated by enabling Server-side Pagination in BREAD and then having a relationship field.

Now upon searching the relationship field in browse view, an exception occurs.

This fixes fixes duplicate filter field occurance and enables multiple relationship fields sharing same reference column

This also fixes the duplicate filter dropdown entries when there is a non-relation field sharing the same name with a relationship reference column name in the same BREAD.

Note that this will not affect multiple relation fields in a BREAD sharing the same relationship reference column name (but different display column for instance).

This allows use of custom relationship methods in eloquent models

If you are using a custom relationship method in your eloquent model, you can mention that method name in Relationship Details as long as you have specified your model in BREAD.

public function group()
{
    return $this->belongsTo(\TCG\Voyager\Facades\Voyager::modelClass('Role'), 'role_id');
}

If a name is not specified, the relationship method name will be determined from the model name.

[pckz]

awesome work! thanks @samiksengupta
please @eclairAB review this PR 🙏